This invention relates to a metal injection molding method of manufacturing an object having a desired shape, such as a form tool for forming threaded fasteners.
Form tools for forming threaded fasteners (hereinafter referred to as xe2x80x9cthreaded fastener form toolsxe2x80x9d) are well-known in the threaded fastener industry. A few examples of the many known types of threaded fastener form tools are shown in FIGS. 1A-5. Specifically, FIGS. 1A-2B illustrate two punch-type threaded fastener form tools used for impact forming threaded fastener heads. More specifically, FIGS. 1A and 1B illustrate a threaded fastener form tool 10 for forming a flat head with a TORX type drive on a threaded fastener, while FIGS. 2A and 2B illustrate a threaded fastener form tool 12 used for forming a flat head with a PHILLIPS type drive on a threaded fastener. FIGS. 3A and 3B illustrate another form of punch-type threaded fastener form tool used to finish the head and TORX-type drive on a threaded fastener. While only three examples are illustrated, it will be appreciated that similar punch-type form tools can be used to form other types of threaded fastener heads, such as for example, round heads, fillister heads, oval heads, hexagon heads, and socket heads, as well as other types of drives, such as for example, hex socket, drilled spanner, fluted socket, slotted spanner, slotted, clutch, pozi drive, and one-way. FIGS. 4A and 4B illustrate a so-called xe2x80x9ctri-lobularxe2x80x9d form tool 14 and FIG. 5 illustrates a rolling thread type flat form tool 16 for forming the threads on a threaded fastener. While only two examples are illustrated, it will be appreciated that there are a number of other types of form tools used for forming the threads and shank of a threaded fastener.
Typically, threaded fastener form tools must produce a large number of threaded fasteners at a relatively high production rate to provide an economically feasible product. Additionally, the threaded fasteners are often formed from high strength materials and the features of the threaded fasteners must be held to relatively tight tolerances to provide the desired capabilities and quality for the threaded fasteners. Further, many of the threaded fasteners have relatively intricate, small scale features that must be mirrored on the threaded fastener form tools as shown by the examples in FIGS. 1A-2B. In view of these factors, threaded fastener form tools are typically made from materials having very high strength and hardness and must be manufactured with great precision in order to produce threaded fasteners having the desired features, capabilities and quality. Conventionally, such threaded fastener form tools are manufactured by highly skilled machinists using precision machining operations or from wrought metal material. While this method of manufacture produces acceptable threaded fastener form tools, it is relatively expensive and time-consuming.
It is a primary object the invention to provide a new and improved method of manufacturing an object having a desired shape, such as a threaded fastener form tool.
According to one embodiment of the invention, the method includes the steps of preparing a feedstock of powdered metal and binder; heating and injecting the feedstock into a mold having an over-sized, negative image of the threaded fastener form tool; hardening the feedstock in the mold to form a green part; removing the green part from the mold; reworking the green part to alter at least one of the shape and size of the green part; debinding the green part to form a debound part; and sintering the debound part to form a densified part having at least the near net shape of the threaded fastener form tool.
According to another embodiment of the invention, a method is provided for manufacturing an object having a desired shape. The method includes the steps of preparing a feed stock of powdered metal and binder; heating and injecting the feed stock into a mold having an over-sized, negative image of the object; hardening the feed stock in the mold to form a green part; removing the green part from the mold; placing the green part in inventory; removing the green part from inventory; and reworking the green part to modify at least one of the shape and size of the green part.
In accordance with one form of the invention, the method further includes the steps of heat treating and/or finish machining the threaded fastener form tool after the sintering step.
According to another embodiment of the invention, the method includes the steps of loading a powdered metal mixture into a compression mold having a negative image of the threaded fastener form tool; compressing the powdered metal mixture in the compression mold to form a green part having at least the near net shape of the threaded fastener form tool; removing the green part from the compression mold; and sintering the green part to form a densified part having at least the near net shape of the threaded fastener form tool.
Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings.